Surface temperature and ozone responses to the 2030 Global Methane Pledge

Abstract

The emissions of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) continue to rise, and the effects of global warming are becoming increasingly evident. While efforts to mitigate climate change generally focus on CO2, reducing methane emissions is considered a particularly effective approach to moderate global warming in the coming decades because methane has a shorter atmospheric lifetime. The Global Methane Pledge (GMP), announced in September 2021, urges countries to reduce anthropogenic methane emissions by 30% (relative to 2020 levels) by 2030, aiming to prevent an estimated 0.2 °C global temperature increase. This could buy time to curb the growth of atmospheric CO2 concentrations. However, there is doubt regarding the ability to fulfil the GMP in time, and its impact on the atmosphere and climate is uncertain. We used an Earth system model with a mixed-layer ocean and interactive atmospheric chemistry, driven by temporally changing methane emissions, to explore future climate and air quality responses to different methane reduction strategies. We find reducing methane emissions decelerates global warming through changes in radiative fluxes and shortening the lifetime of tropospheric methane and other gases. A coincident air quality improvement is expected from a reduction of ozone near the surface. Our model results indicate that the full climate response to reduced methane emissions has a lag of two to three decades, indicating the urgency of implementing the GMP. While further measures will be required to reach the goals of the Paris Agreement and avoid irreversible climate change, achieving the GMP would provide significant progress toward global decarbonization efforts.